End effector for carrying wafer or wafer assembly

Abstract

An end effector for carrying a wafer or wafer assembly placed thereon is provided. The end effector is integrated with or configured to attach to the robotic arm. The end effector includes a peripheral mount located radially outside of the base portion, the peripheral mount including at least a first mounting section and a second mounting section, e.g., disposed on opposite sides of the base portion. The base portion has a substantially flat horizontal upper surface. Each mounting section of the peripheral mount has a substantially flat horizontal upper surface raised relative to the upper surface of the base portion. The end effector is thereby configured to hold a wafer assembly at a first height above the base portion that bridges an upper surface of the mounting section. There is a stepped region between the base portion and each mounting section of the peripheral mount. Each step region includes a support surface raised relative to an upper surface of the base portion. The end effector is thereby configured to hold the wafer bridging the support surface at a second height above the base portion.

Description

Technical Field

[0001] The present invention generally relates to end effectors for transporting individual wafers and wafer assemblies before, after, or during processing. The present invention also relates to semiconductor processing apparatuses incorporating such end effectors, and methods of transporting wafers and wafer assemblies. Background Art

[0002] Wafers to be processed are typically transported by a robotic arm having an end effector that supports and holds the wafer. In plasma cutting applications, the wafers to be cut tend to be attached to carriers suitable for retaining the individual semiconductor die after separation. Such wafer assemblies include wafers supported by a film / tape in a frame, and wafers mounted on a silicon or glass substrate.

[0003] The handling and transportation of wafer assemblies tend to be via a dedicated robotic arm having an end effector with a suitable configuration that operates on a specific wafer carrier type, size, and shape. In configurations where the wafers are supported by a film / tape and a frame, the end effector tends to contact the frame or tape, but avoids contacting the tape under the wafer, such that the die are not accidentally displaced after cutting. The advantage of using a dedicated robotic arm is to avoid cross-contamination between different wafer assemblies.

[0004] US9343365B2 describes a method and apparatus for plasma cutting semiconductor wafers, in which wafers supported by a tape and a frame are transferred into and out of a process chamber by a transfer arm. The transfer arm has a central recess such that it contacts the frame while avoiding contact with the tape directly under the substrate wafer.

[0005] US9446522B2 describes an arrangement in which a wafer carrier ring is supported by tines of an end effector that contact the ring but avoid contacting the wafer substrate on the carrier.

[0006] There is a desire in the art for a multi-purpose end effector that can operate on different wafer and wafer assembly types without the need for reconfiguration or replacement, while protecting the wafers from contamination. This multi-functional end effector will have particular utility in vacuum transport applications where reconfiguring the tool may be more difficult and / or expensive. Summary of the Invention

[0007] In a first aspect of the present invention, there is provided an end effector for carrying a wafer or wafer assembly placed thereon, the end effector being integrated with or configured to be attached to a robotic arm. The end effector includes a peripheral mount circumferentially arranged around a base portion, the peripheral mount including at least a first mounting section and a second mounting section. The base portion has a generally flat horizontal upper surface, and each mounting section of the peripheral mount has a generally flat horizontal upper surface raised relative to the upper surface of the base portion, whereby the end effector is configured to hold, at a first height above the base portion, a wafer assembly bridging the upper surfaces of the mounting sections. There is a step region between the base portion and each mounting section of the peripheral mount. Each step region includes a support surface raised relative to the upper surface of the base portion, whereby the end effector is configured to hold, at a second height above the base portion, a wafer bridging the support surfaces.

[0008] The present invention thereby provides an end effector that can carry both wafers and wafer assemblies (although not necessarily simultaneously). Accordingly, the present invention provides a dual-functional end effector that obviates the need to change tools during wafer bonding, etching, and other processes. The end effector of the present invention enables rapid switching between wafer-carrying and wafer-assembly-carrying applications, provides versatility compared to prior art end effectors, and saves time and cost in semiconductor production.

[0009] Furthermore, the end effector according to the present invention prevents metal cross-contamination between wafers and wafer assemblies carried on the device, since the wafers and wafer assemblies are supported on different horizontal planes. Additionally, the end effector of the present invention minimizes interference with the wafer substrate by providing a vertical separation between the base portion and the wafer or wafer assembly placed on the device.

[0010] In the context of the present invention, a "wafer" will be considered to include a wafer mounted on a support wafer, such as a silicon wafer mounted on a glass wafer. The wafer may also be unloaded. The support wafer typically may have the same or a similar size as the wafer, e.g., a diameter of 200 mm or 300 mm. The wafer is preferably a circular wafer.

[0011] In the context of the present invention, a "wafer assembly" will be considered to include a wafer mounted on a film / tape supported in a frame. For example, the wafer assembly may preferably be a generally circular wafer assembly, wherein the circular wafer is supported on a generally circular frame.

[0012] The base portion may be generally circular or include, for example, a portion of a circle with truncated sides. The upper surface of the base portion may include a continuous flat surface, or there may be one or more cutout regions of the base portion. The mounting sections may be arranged on opposite sides of the base portion, for example, the mounting sections may be diametrically opposite across the upper surface of the base portion. Alternatively, the mounting sections may not be diametrically opposite, for example, positioned at a 90-degree angle to each other around the imaginary center point of the base portion. In this context, "on opposite sides" will be understood to mean different circumferential positions around the perimeter of the base portion.

[0013] There may be more than two, for example three or more, mounting sections. The mounting sections may be included in one continuous body or may be discrete mounting sections.

[0014] The mounting sections and the corresponding stepped regions may be symmetric across the base portion.

[0015] The end effector may include two spaced-apart forks extending from a connector body, where the connector body is configured to be attached to a robotic arm.

[0016] The connector body may include a toothed edge (i.e., include a plurality of notches in the end face) for connection to a robotic arm having a connection face with a complementary shape. The connector body may alternatively include a different type of connector for attachment to the robotic arm.

[0017] The connector body may include a mounting section, and each fork may include another mounting section (as well as a corresponding portion of the base portion). Each another mounting section may be at the distal end of the connector body.

[0018] The forks may narrow from the connector body towards the distal end.

[0019] The boundary line between the stepped region and the base portion may be defined by a circumferential arc. In an arrangement where the end effector is configured (i.e., sized and shaped appropriately) to carry a 300 mm wafer or a 300 mm wafer assembly, the radius of the circumferential arc may be 146 to 150 mm taken from the imaginary center point of the base portion.

[0020] The boundary line between the stepped region and the peripheral mount may be defined by a circumferential arc. In an arrangement where the end effector is configured (i.e., sized and shaped appropriately) to carry a 300 mm wafer or a 300 mm wafer assembly, the radius of the circumferential arc may be 150 to 154 mm from the imaginary center point of the base portion.

[0021] The upper surface of the peripheral mount may extend a length of at least 15 mm (e.g., 20 mm) in a direction parallel to the central longitudinal axis of the end effector and beyond the boundary line between the stepped region and the peripheral mount. The length of at least 15 mm may enable support and transportation of various wafer assembly types and sizes (e.g., non-standard frame sizes).

[0022] The first height can be from 1 to 5 mm. The second height can be from 0.1 to 3 mm. The first height can be greater than the second height.

[0023] The support surface can include a flange.

[0024] In a direction parallel to the central longitudinal axis of the end effector, the length of the flange can be from 0.2 to 0.6 mm, such as 0.4 mm.

[0025] A length of at least 0.2 mm can be sufficient to support the wafer edge while minimizing the overall size of the end effector.

[0026] The support surface can include a convex surface. The convex surface can enable the tape of the wafer assembly supported on the end effector to rest on a smooth surface in which there are no sharp edges or corners under the tape.

[0027] The flange can be adjacent to the base portion, and the convex surface can be adjacent to the flange and the peripheral mount.

[0028] The convex surface can be defined by an arc with a radius of 2.5 to 3.5 mm.

[0029] The base portion can have a depth of 3 mm in a direction orthogonal to its upper surface.

[0030] The end effector can be formed of a ceramic material. The end effector can be formed of a metal.

[0031] The end effector can be formed of a metal coated with an electrostatic discharge material.

[0032] In a second aspect, there is provided a semiconductor processing apparatus including a robotic arm and an end effector. The end effector is integrated with or attached to the robotic arm. The end effector includes a peripheral mount radially outside a base portion, the peripheral mount including at least a first mounting section and a second mounting section. The base portion has a generally flat horizontal upper surface, and each mounting section of the peripheral mount has a generally flat horizontal upper surface that is elevated relative to the upper surface of the base portion. The end effector is thereby configured to hold a wafer assembly bridging the upper surfaces of the mounting sections at a first height above the base portion. There is a step region between the base portion and each mounting section of the peripheral mount. Each step region includes a support surface that is elevated relative to the upper surface of the base portion. The end effector is thereby configured to hold a wafer bridging the support surfaces at a second height above the base portion.

[0033] In a third aspect, a method of transporting a wafer using a semiconductor processing apparatus is provided. The semiconductor processing apparatus includes a robotic arm and an end effector according to the first aspect of the present invention. The end effector is integrated with or attached to the robotic arm. The method includes the steps of placing the wafer on the end effector such that the wafer bridges the support surface of each step region; and transporting the wafer by moving the robotic arm.

[0034] In a fourth aspect, a method of transporting a wafer assembly using a semiconductor processing apparatus is provided. The semiconductor processing apparatus includes a robotic arm and an end effector according to the first aspect of the present invention. The end effector is integrated with or attached to the robotic arm. The method includes the steps of placing the wafer assembly on the end effector such that the wafer assembly bridges the upper surface of each mounting section; and transporting the wafer assembly by moving the robotic arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Embodiments of the present invention will now be described, by way of example only, with reference to the schematic drawings:

[0036] Figure 1 is a perspective view of a wafer according to an exemplary embodiment of the present invention;

[0037] Figure 2 is a perspective view of a wafer assembly according to an exemplary embodiment of the present invention;

[0038] Figure 3 is a perspective view of an end effector according to an exemplary embodiment of the present invention;

[0039] Figure 4 is a top view of an end effector according to an exemplary embodiment of the present invention;

[0040] Figure 5 is a side view of an end effector according to an exemplary embodiment of the present invention;

[0041] Figure 6 is a side view of an end effector according to an exemplary embodiment of the present invention supporting a wafer on a carrier; and

[0042] Figure 7 is a side view of an end effector according to an exemplary embodiment of the present invention supporting a wafer on a thin film and a frame. DETAILED DESCRIPTION

[0043] The wafer 1a to be transported ( Figure 1) includes a circular silicon wafer 3a on a circular glass substrate 4. The silicon wafer has a diameter d1 of 300 mm. The glass substrate 4 has a corresponding diameter d2 of 300 mm (but may have a diameter greater than that of the wafer 3a in alternative embodiments). In alternative embodiments, the wafer 3a may be unsupported or may be supported on a different carrier (such as a silicon substrate). Alternatively, in different embodiments, the wafer may have different sizes, for example, the wafer may include a circular wafer with a diameter of 200 mm.

[0044] The wafer assembly 1b to be transported ( Figure 2 ) includes a 300 mm circular silicon wafer 3b resting on a tape 5 supported in a frame 7 (i.e., a tape and frame assembly 4). The wafer 3b, the tape 5, and the frame 7 are arranged concentrically, and the frame 7 is mounted on the tape 5 and has a circular inner perimeter with a diameter d3 of 350 mm. In an exemplary embodiment, the outer perimeter of the frame 7 is circular and the edges are chamfered such that it has a thicker edge in the opposite lateral directions (x, y) across the assembly (i.e., the outer perimeter of the frame 7 is not precisely circular). The non-circular outer perimeter of the frame 7 has a maximum diameter d4 of 400 mm. The wafer frame may, for example, meet the SEMI G87 or G74 300 mm wafer frame specifications. Alternatively, in different embodiments, the wafer assembly may have a size and shape for holding wafers of different sizes. For example, in an embodiment where the wafer is a 200 mm circular silicon wafer, the wafer frame may have a circular inner perimeter with a diameter of 250 mm and an outer perimeter with a maximum diameter of 300 mm.

[0045] An end effector 11 according to an exemplary embodiment of the present invention ( Figure 3 ) is configured to interchangeably carry the wafer 1a and the wafer assembly 1b described above. The end effector 11 of the exemplary embodiment is formed of titanium coated with a non-electrostatic discharge coating and is shaped such that the wafer 1a and the wafer assembly 1b are supported on different horizontal planes to contact different parts of the end effector 11. In an exemplary embodiment, the non-electrostatic discharge coating includes diamond-like carbon, but in alternative embodiments, it may include different non-electrostatic discharge materials. In another embodiment, the end effector may be formed of aluminum or a different material.

[0046] The end effector 11 includes a peripheral mount 13 that is arranged around a recessed base portion 15 as three discrete mounting sections 13a, 13b, 13c. The base portion 15 is generally planar and has a flat upper surface 17 along a first horizontal plane. Each mounting section 13a, 13b, 13c of the peripheral mount has a flat upper surface 19a, 19b, 19c along a second, elevated, horizontal plane.

[0047] The end effector 11 has a fork shape. The end effector 11 includes a connector body 21 that is integrally formed with a first mounting section 13a of a peripheral mount and extends outwardly from the first mounting section 13a of the peripheral mount along a central longitudinal axis L. The connector body 21 includes a toothed end section 23 that is shaped to interconnect with a complementary shaped connector of a robotic arm (not shown).

[0048] The end effector 11 includes two fork heads 25a, 25b that extend from the first mounting section 13a in a direction parallel to the central longitudinal axis L. The end effector 11 is symmetric about the central longitudinal axis L. Each fork head 25a, 25b includes a respective portion 15a, 15b of the base portion 15. Each fork head 25a, 25b includes mounting sections 13b, 13c at the distal end 26 of the connector body 21. The second and third mounting sections 13b, 13c include rounded end faces 27.

[0049] Generally, in an exemplary embodiment for transporting 300 mm wafers and 300 mm wafer assemblies, the end effector 11 has a length L1 of 410 to 450 mm, a width W1 of 100 to 175 mm, and a depth D1 of 6 mm. The width W1 of the end effector remains constant along its length. Each fork head 25a, 25b has a width W2 that decreases with the distance from the connector body 21 towards the distal end 26. In other words, the lateral separation between the fork heads increases towards the distal end. In other embodiments of the present invention, the dimensions of the end effector may be appropriately scaled to transport different sized wafers / wafer assemblies, such as 200 mm wafers / wafer assemblies.

[0050] The depth of the end effector 11 varies along its length. The horizontal plane of the upper surface 17 of the base portion 15 is recessed relative to the horizontal plane of the upper surface of the peripheral mount 13. More specifically, the horizontal plane of the upper surface 17 of the base portion 15 is recessed relative to the horizontal planes of the upper surfaces 19a, 19b, 19c of the mounting sections 13a, 13b, 13c of the peripheral mount 13.

[0051] The end effector 11 includes a step region 29 ( Figure 4 ) between the base portion 15 and the peripheral mount 13. In a top view, the perimeter of the base portion 15, as constituted by each of the two fork heads 25a, 25b, is defined by a circle with a radius of 152 mm (from a hypothetical center point of the base portion 15). The circle is truncated on each of the upper side 31 and the lower side 33 of the end effector, such that the base portion 15 is defined by the middle portion of the circle. In other words, the footprint of the base portion 15 fits within a hypothetical circle with a radius of 152 mm. The step region 29 includes a ring with a breadth of 4 mm, defined by the base portion 15 on an inner circular perimeter 35 and by the peripheral mount 13 on an outer circular perimeter 37.

[0052] In a cross-sectional side view ( Figure 5 ), the stepped region 29 includes an inner square step 39 having a flat upper surface 41 (i.e., a horizontal flange) and an outer rounded step 43 having a top surface 45 defined by an arc with a radius of 3 mm. The base portion 15 has a constant depth D2 of 3 mm. Each mounting section 13a, 13b, 13c has a constant depth D1 of 6 mm. The connector body 21 (best shown in Figure 3 ) has a constant depth of 3 mm that extends below the horizontal plane of the upper surface 13a. The square step 39 (referring again to Figure 5 ) has a depth D3 of 3.4 mm (i.e., the upper surface 41 of the square step 39 is 0.4 mm higher than the upper surface 17 of the base portion 15). The top surface 45 of the rounded step 43 forms a convex surface that projects outward from the peripheral mount 13, meets the square step 39 at the inner edge 47, and forms a platform with the upper surface 19a of the first mounting section 13a. The square step 39 has a length L2 of 0.4 mm between the inner edge 47 and the step edge 49. The stepped region 29 has the same profile at each of the mounting sections 13a, 13b, 13c, facing inwardly towards the base portion 15. The stepped regions associated with the second and third mounting sections 13b, 13c are opposite and symmetrically arranged with respect to the stepped region associated with the first mounting section 13a, such that the upper surfaces of each square step are in the same hierarchical horizontal plane. The upper surfaces 19a, 19b, 19c of each of the mounting sections 13a, 13b, 13c are in the same hierarchical horizontal plane, elevated with respect to the upper surface 41 of each square step 39.

[0053] During use, the wafer 1a is supported on the end effector 11, to be transported ( Figure 6 ). The first edge region 51 of the wafer 1a rests on the upper surface 41 of the square step 39 associated with the first mounting section 13a. The second and third edge regions of the wafer 1a rest on the upper surfaces of the square steps associated with the second and third mounting sections (not shown in Figure 6 ). Thus, the wafer 1a is supported on the end effector 11 in a horizontal plane that is 0.4 mm above the upper surface 17 of the base portion 15. In other words, there is a gap 53 above the base portion 15, and the wafer 1a is suspended above the gap 53. In an exemplary embodiment of the present invention, the square step 39 has a length L2 of 0.4 mm, and it has been found that this length provides an optimal contact area to enable the wafer to be supported while being held at a certain distance above the upper surface 17 of the base portion 15.

[0054] Alternatively, during use, the wafer assembly 1b is alternatively supported on the end effector 11, to be transported (Figure 7 )。The first edge region 55 of the wafer assembly 1b is rested on the first mounting section 13a. The second edge region of the wafer assembly 1b is rested on the second mounting section 13b ( Figure 7 not shown). The third edge region of the wafer assembly 1b is rested on the third mounting section 13c ( Figure 7 not shown). Thus, the frame 7 is supported on the end effector 11. The first edge region 55 of the wafer assembly 1a includes the first part 7a of the frame 7 and the first extended part 5a of the tape 5. The first part 7a of the frame 7 is rested on the upper surface 19a of the first mounting section 13a. The first extended part 5a of the tape 5 is partly rested on the upper surface 19a of the first mounting section 13a and partly rested on the top surface 45 of the rounded step 43 of the stepped region 29. Similar arrangements are provided at the second and third mounting sections 13b, 13c. By the friction between the lower side of the tape 5 and the top surface 45 of the rounded step 43 (at each mounting section) and the upper surfaces 19a, 19b, 19c of the mounting sections 13a, 13b, 13c, the wafer assembly 1b is firmly held in place on the end effector 11.

[0055] The inner edge 58 of the first section 7a of the frame 7 that is rested on the upper surface 19a of the first mounting section 13a is shifted backward by a length L3 of about 20 mm from the outer edge 56 of the rounded step 43. The outer edge 59 of the first section 7a of the frame 7 is shifted backward by a length L4 of about 40 mm from the outer edge 56 of the rounded step 43. Corresponding arrangements (i.e., mirror reflections) are provided at the second and third mounting sections 13b, 13c. Advantageously, according to the present design, the mounting sections 13a, 13b, 13c have sizes and shapes that accommodate not only standard 300 mm wafer frames but also non-standard 300 mm wafer frames. The frame of a non-standard 300 mm wafer assembly can still be rested on the upper surfaces of the mounting sections 13a, 13b, 13c, but the frame can be shifted backward by different amounts from the outer edge 56 of the rounded step 43, i.e., the length L3 can vary, but the tape and the frame will still be adequately supported.

[0056] In an embodiment where the wafer is a 200 mm wafer and the wafer assembly is a 200 mm wafer assembly, the dimensions of the step region and the mounting section may be comparable to those of the example embodiments associated with a 300 mm wafer. However, the radius of the circumferential line defining the inner boundary of the step region (taken from the imaginary center point of the base portion) is correspondingly reduced. The overall length and width of the end effector L1, W1 will be reduced. However, the length of the square step L2 will remain unchanged, and the size of the rounded step 43 and the length of the upper surfaces 19a, 19b, 19c of the mounting section will also remain unchanged. Each of the mounting sections 13a, 13b, 13c has a length sufficient to accommodate a non-standard wafer assembly (whether it is a 300 mm wafer assembly or a 200 mm wafer assembly).

[0057] In the example embodiment, the tape 5 in each edge region 55 of the wafer assembly 1b follows the contour of the upper surface 19a of the first mounting section 13a and the top portion 60 of the top surface 45 of the rounded step 43 before being flattened into a horizontal plane. Thus, the tape 5 spans each of the mounting sections 13a, 13b, 13c and the rounded steps 43 of the corresponding step regions and follows a smooth profile, and there are no sharp edges or corners under the tape 5.

[0058] Each edge region of the wafer assembly 1b rests on the upper surfaces of the mounting sections 13a, 13b, 13c and on the corresponding step regions (not shown). Thus, the wafer 1b is supported on the end effector 11 in a horizontal plane at a height 3 mm above the upper surface 17 of the base portion 15. In other words, there is a gap 57 above the base portion 15, and the wafer assembly 1b is suspended above the gap 57.

Claims

1. An end effector for carrying a wafer or wafer assembly placed thereon, the end effector being integrated with or configured to be attached to a robotic arm; The end effector includes a peripheral mount arranged circumferentially around a base portion, the peripheral mount including at least a first mounting section and a second mounting section; The base portion has a generally flat horizontal upper surface, and each mounting section of the peripheral mount has a generally flat horizontal upper surface raised relative to the upper surface of the base portion, whereby the end effector is configured to hold a wafer assembly bridging the upper surfaces of the mounting sections at a first height above the base portion; There is a step region between the base portion and each mounting section of the peripheral mount; Each step region includes a support surface raised relative to the upper surface of the base portion, whereby the end effector is configured to hold a wafer bridging the support surface at a second height above the base portion.

2. The end effector according to claim 1, comprising two spaced apart forks extending from a connector body, wherein the connector body is configured to be attached to the robotic arm.

3. The end effector according to claim 2, wherein the connector body includes a mounting section, and each fork includes a portion of the base portion and another mounting section, the another mounting section being at the distal end of the connector body.

4. The end effector according to claim 2 or 3, wherein the forks narrow from the connector body towards the distal end.

5. The end effector according to any one of claims 1 to 3, configured to carry a 300 mm wafer or 300 mm wafer assembly, wherein the boundary line between the step region and the base portion is defined by a circumferential arc with a radius of 146 to 150 mm from the imaginary center point of the base portion.

6. The end effector according to any one of claims 1 to 3, configured to carry a 300 mm wafer or 300 mm wafer assembly, wherein the boundary line between the step region and the peripheral mount is defined by a circumferential arc with a radius of 150 to 154 mm from the imaginary center point of the base portion.

7. The end effector according to any one of claims 1 to 3, wherein the upper surface of the peripheral mount extends in a direction parallel to the central longitudinal axis of the end effector for a length of at least 20 mm beyond the boundary line between the step region and the peripheral mount.

8. The end effector according to any one of claims 1 to 3, wherein the first height is 1 to 5 mm.

9. The end effector according to any one of claims 1 to 3, wherein the second height is 0.1 to 3 mm.

10. The end effector according to any one of claims 1 to 3, wherein the first height is greater than the second height.

11. The end effector according to any one of claims 1 to 3, wherein the support surface includes a flange.

12. The end effector according to claim 11, wherein the flange has a length in a direction parallel to the central longitudinal axis of the end effector of 0.2 to 0.6 mm.

13. The end effector according to any one of claims 1 to 3, wherein the support surface includes a convex surface.

14. The end effector according to claim 11, wherein the flange is adjacent to the base portion, and the convex surface abuts the flange and the peripheral mounting member.

15. The end effector according to claim 13, wherein the convex surface is defined by an arc having a radius of 2.5 to 3.5 mm.

16. The end effector according to any one of claims 1 to 3, wherein the base portion has a depth of 3 mm in a direction orthogonal to its upper surface.

17. The end effector according to any one of claims 1 to 3, wherein the end effector is formed of a ceramic material or a metal.

18. The end effector according to any one of claims 1 to 3, wherein the end effector is formed of a metal coated with an electrostatic discharge material.

19. A semiconductor processing apparatus including a robotic arm and an end effector; The end effector is integrated with or attached to the robotic arm; The end effector includes a peripheral mounting member radially disposed outside the base portion, and the peripheral mounting member includes at least a first mounting section and a second mounting section; The base portion has a generally flat horizontal upper surface, and each mounting section of the peripheral mounting member has a generally flat horizontal upper surface raised relative to the upper surface of the base portion, whereby the end effector is configured to hold a wafer assembly bridging the upper surfaces of the mounting sections at a first height above the base portion; There is a stepped area between the base portion and each mounting section of the peripheral mounting member; Each stepped area includes a support surface raised relative to the upper surface of the base portion, whereby the end effector is configured to hold a wafer bridging the support surface at a second height above the base portion.

20. A method of transporting wafers using a semiconductor processing apparatus, the semiconductor processing apparatus including a robotic arm and an end effector according to any one of claims 1 to 18, the end effector being integrated with or attached to the robotic arm, the method comprising the steps of: Placing the wafer on the end effector such that the wafer bridges the support surface of each stepped area; Transporting the wafer by moving the robotic arm.

21. A method of transporting a wafer assembly using a semiconductor processing apparatus, the semiconductor processing apparatus including a robotic arm and an end effector according to any one of claims 1 to 18, the end effector being integrated with or attached to the robotic arm, the method comprising the steps of: Placing the wafer assembly on the end effector such that the wafer assembly bridges the upper surfaces of each mounting section; Transport the wafer assembly by moving the robotic arm.

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